The present invention relates to an optical repeater which is used in an optical network, for amplifying an optical signal being transmitted, and an optical network using an optical repeater.
A conventional submarine repeatered transmission network employing a submarine optical fiber cable, for example, requires a submarine optical repeater which amplifies an attenuated optical signal for long distance transmission. FIG. 1 is a block diagram showing the constitution of the submarine optical repeater for use in the conventional optical network.
In FIG. 1 a submarine optical cable 51 comprises an optical fiber 52 for transmitting an optical signal and a feed line 57 for supplying power necessary for repeater processing. A submarine optical repeater 50 which is inserted in the submarine optical cable 51 at predetermined intervals comprises an optical/electrical converter 53 for converting the optical signal into an electrical signal, an amplifier 55 for amplifying the electrical signal, an electrical/optical converter 54 for converting the amplified electrical signal into an optical signal for input into the optical fiber 52, and a power circuit 56 for supplying power to the converters 53 and 54, and the amplifier 55.
Thus, the submarine optical repeater 50 of the conventional optical network has an arrangement in which an attenuated optical signal is converted into an electrical signal, which is amplified and is then converted again into an optical signal for output at a high signal level.
In such a submarine optical repeater 50 it is necessary for the amplification of the optical signal to supply an appreciable amount of power to each circuit. This inevitably calls for the use of a feed line of an excellent insulating property, for instance, from a power feed unit on land to the submarine optical repeater 50.
Moreover, the submarine optical repeater 50 must be highly reliable for its long-term, maintenance-free operation. However, since each circuit of the conventional submarine optical repeater 50 includes many parts involving semiconductor devices, the individual parts must be made very highly reliable for obtaining the required reliability--this inevitably makes the submarine optical repeater 50 expensive and hence increases the manufacturing costs of the entire optical network.